High-pressure pneumatic and liquid injection apparatus

ABSTRACT

A pressurized working environment for a pneumatic device which permits emission-free utilization of the potential mechanical energy of pressure differentials within compressed gas systems is disclosed. The pneumatic device is contained within a pressure vessel and the pneumatic device exhaust is in fluid communication with the interior of the pressure vessel. In use, the interior of the pressure vessel is in fluid communication with an area of lower pressure in the compressed gas system and the pneumatic device intake is in fluid communication with an area of higher pressure in the compressed gas system. In use, the gas from the area of higher pressure drives the pneumatic device and is then exhausted to the area of lower pressure.

[0001] This application is a division of U.S. application Ser. No.09/598,917, filed Jun. 22, 2000, which claimed the benefit of U.S.Provisional Application No. 60/140,904, filed Jun. 23, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates to compressed gas in situationswhere, in utilizing the potential energy of the compressed gas throughpneumatic devices, it is preferable to recover the gas exhausted fromthe pneumatic device, including, but not limited to, natural gasproduction facilities and wells. The present invention also relates tothe injection of liquids into compressed gas.

BACKGROUND OF THE INVENTION

[0003] In many situations it is necessary to utilize the potentialenergy of a compressed gas to power pneumatic devices so as to driveequipment. Pneumatic devices are devices which operate by converting thepotential mechanical energy of a compressed gas into motion. Pneumaticdevices utilize the tendency of gases to flow from an area of higherpressure to an area of lower pressure and therefore they require apressure differential in order to operate. Typically, this pressuredifferential is between the exterior of the pneumatic device, typicallythe atmosphere, and a supply of gas at a higher than atmosphericpressure, which is fed into the interior of some of the components ofthe pneumatic device.

[0004] In general terms, the components of a pneumatic device may bedivided into pressure differential components and non-pressuredifferential components. The pressure differential components are thosecomponents of a pneumatic device which face a pressure differentialbetween their interiors and exteriors during normal operation. Examplesof pressure differential components include: pipes and other forms ofgas conduits; pneumatic cylinders; and valves. Non-pressure differentialcomponents are those components of a pneumatic device which do not facea pressure differential between their interiors and exteriors duringnormal operation. Examples of non-pressure differential componentsinclude: power output means such as shafts; and switch linkages.

[0005] In natural gas production facilities, it is often necessary toperiodically or continually inject liquids into a high pressure gaspipeline. An example is methanol, which may be injected to prevent anywater present in the natural gas from freezing. Such liquids areinjected by means of pumps which overcome the pressure of the compressedgas to force the liquid into the pipeline. These injection pumps areoften powered by pneumatic devices, particularly in remote locations. Insome situations, the compressed gas flowing in the pipeline is used todrive the pump, but typically, only after it has been regulated down toa pressure suitable for the pneumatic device, often around 10 pounds persquare inch. The exhaust gas from the pneumatic device comes out of thedevice at a lower pressure than the gas in the pipeline, so it can't bereinjected into the pipeline unless it is first compressed. Thereforethe exhaust gas is usually vented to atmosphere. In some situations agas such as propane is brought to the site, stored in a pressure vessel,and used to drive a pneumatic device. This gas is also vented toatmosphere from the pneumatic device.

[0006] This venting of the exhaust gas to atmosphere is a problembecause it is a waste of valuable gas and because it raisesenvironmental concerns, particularly in the case of sour gas. A means ofutilizing the potential energy of the compressed gas, and of injectingliquids into a high pressure gas pipeline, which does not requireventing of the gas is required.

BRIEF SUMMARY OF THE INVENTION

[0007] In accordance with the invention, it is found in using pneumaticdevices that pressurizing the work environment of a variety of pneumaticdevices and containers to the same pressure as the compressed gas withwhich the devices and containers are associated produces many benefits,including, but not limited to, the emission-free operation of pneumaticdevices and the efficient injection of liquids into compressed gases.

[0008] In accordance with the invention, if a pressure differentialexists within a compressed gas system, in a natural gas pipeline forexample, and the working environment of the pneumatic device ispressurized by means of direct contact with that compressed gas in thecompressed gas system which is at the lower pressure, and the pneumaticdevice is driven by compressed gas from that portion of the compressedgas system which is at the higher pressure, then the pneumatic devicecan operate so as to exhaust gas back into the compressed gas system;and the pressure differential components of the pneumatic device willface a maximum pressure differential between their interiors andexteriors equal to the pressure differential within the compressed gassystem, rather than the pressure differential between the compressed gassystem and the atmosphere.

[0009] Natural gas often comes out of the well at a high pressure, forexample, 1,000 pounds per square inch. The natural gas often undergoessome processing immediately downstream of the well, for example, wateris often removed by running the gas through a dehydrator. A usual sideeffect of this processing is that it lowers the pressure of the gasdownstream of the processing equipment relative to the pressure upstreamof the processing equipment, typically by constricting the flow of thegas. Therefore, there is usually a pressure differential between the gasupstream of the processing equipment and the gas downstream of theprocessing equipment. In situations where there is no processingequipment, a similar pressure differential can be created merely byconstricting the flow of the gas.

[0010] One embodiment of this invention receives gas from the upstream,higher pressure side of the processing equipment, uses it to power apneumatic device and then exhausts the gas at a pressure high enough sothat the gas can be reinjected at the downstream, lower pressure side ofthe processing equipment.

[0011] A feature of this invention is a pressure vessel strong enough towithstand the highest pressure found in the compressed gas system towhich the pressure vessel is attached. The pressure vessel contains someor all of the pressure differential components of a pneumatic device,whereby, although the device operates at a high ambient pressure, suchas 1,000 pounds per square inch, the differential pressure faced by thebodies and seals of the various components (not including those sealsbetween the exterior and interior of the pressure vessel) is low, suchas 25 to 30 pounds per square inch.

[0012] The pneumatic drive unit or pneumatic device can be any devicethat operates by converting the potential mechanical energy of acompressed gas into motion.

[0013] In one embodiment of this invention, the pressure vessel containsa valve means connected by suitable conduit to the relatively higherpressure compressed gas in the pipeline; to a pneumatic cylinder; and tothe interior of the pressure vessel, such that the valve means can beactuated to restrict the flow of gas between two of the three conduitsconnected to the valve means, being between the conduit to therelatively higher pressure compressed gas in the pipeline and theconduit to the pneumatic cylinder; and between the conduit to thepneumatic cylinder and the conduit to the interior of the pressurevessel. The interior of the pressure vessel is connected by suitableconduit to the relatively lower pressure compressed gas in the pipeline,wherein the pressure in the pressure vessel is essentially the same asthe relatively lower pressure compressed gas in the pipeline. Thepneumatic cylinder contains a piston. The piston in the pneumaticcylinder is connected to a spring which acts to move the piston so as toevacuate the compressed gas from the cylinder. The piston in thepneumatic cylinder is connected to a means for actuating the valve meanssuch that when the piston is at the top of its stroke, being theposition of its stroke where the compressed gas is substantiallyevacuated from the pneumatic cylinder, the valve means is actuated topermit the compressed gas to flow from the pipeline to the pneumaticcylinder, and such that when the piston is substantially at the bottomof its stroke, being the position of its stroke where the pneumaticcylinder is substantially full of compressed gas, the valve means isactuated to permit the compressed gas to flow from the pneumaticcylinder to the interior of the pressure vessel. When the valve means isactuated to permit the compressed gas to flow from the pipeline to thepneumatic cylinder, the pneumatic cylinder fills with compressed gas andthe piston moves to the bottom of its stroke. When the pneumaticcylinder is substantially full of compressed gas and the piston is atthe bottom of its stroke, the valve means is actuated to permit thecompressed gas to flow from the pneumatic cylinder to the interior ofthe pressure vessel and the spring pulls the piston to the top of itsstroke evacuating the compressed gas from the pneumatic cylinder to theinterior of the pressure vessel and thence to the relatively lowerpressure portion of the pipeline. In this way the piston is made to movein a reciprocating motion. The piston can be connected to a variety ofmechanical devices such that the reciprocating motion of the piston isused to drive the mechanical device.

[0014] The movement created when the pneumatic device is actuated by thecompressed gas can be transferred to the exterior of the pressure vesselby a variety of mechanical means, such as by a reciprocating shaftpassing through the vessel wall, or by a rotating shaft passing throughthe vessel wall.

[0015] With a shaft passing through the pressure vessel wall where thereis a high pressure differential between the inside and outside of thepressure vessel, a shaft making a rotary movement is easier to seal thana shaft making a reciprocating movement. A feature of this invention isa means of changing a reciprocating movement of a piston into anoscillating rotary movement. In one embodiment, the piston is attachedto one end of a chain, the first chain. The other end of the first chainis attached to the circumferential edge of a wheel. The wheel isconcentrically mounted on a shaft. The shaft is connected to the wallsof the pressure vessel so that it can only move rotationally. A secondchain is also attached to the circumferential edge of the wheel. Thesecond chain is attached to a spring. As the pneumatic cylinder fillswith compressed gas the piston moves from the top of its stroke to thebottom of its stroke and pulls on the first chain which causes the wheelto rotate. This rotation of the wheel pulls on the second chain whichstretches the spring. When the piston reaches the bottom of its strokethe compressed gas in the pneumatic cylinder begins venting to theinterior of the pressure vessel. The spring attached to the second chaincauses the wheel to rotate in the reverse direction to its previousrotation, which acts to pull the piston to the top of its stroke. Whenthe piston reaches the top of its stroke, the compressed gas ceasesventing to the interior of the pressure vessel, compressed gas startsflowing into the pneumatic cylinder and the cycle repeats itself. Inthis way the reciprocating motion of the piston is converted to anoscillating rotary motion of the shaft. The oscillating rotary motion ofthe shaft can be used to drive a mechanical device such as a pump by wayof a pitman or crank arm, or some other suitable device.

[0016] A feature of an embodiment of this invention is the submersion ofthe components in oil or some other suitable liquid, which provideslubrication, minimizes wear and prevents corrosion.

[0017] In one embodiment of this invention, part or all of thecomponents of the equipment which is driven by the pneumatic device arecontained within the pressure vessel. In one embodiment, the equipmentis a pump, and part or all of the components of the pump are containedwithin the pressure vessel. In this embodiment of the invention, a sealbetween the interior and exterior of the pressure vessel for a movingshaft is not necessary.

[0018] In one embodiment of the invention, the valve means is connectedby suitable conduit to: the relatively higher pressure portion of thecompressed gas system; to the pneumatic cylinder; and to an exhaustarea. The exhaust area is an area in fluid contact with the relativelylower pressure portion of the compressed gas system. The exhaust areamay be within the interior of the pressure vessel. However, in somecases it is preferable for the exhaust area to be outside of thepressure vessel. For example, in some cases the compressed gas containsliquids which can tend to precipitate out of the compressed gas and toremain in the pressure vessel. This can be avoided by venting theexhaust gases outside of the pressure vessel. In one embodiment, theexhaust gas is vented within the conduit connecting the pressure vesselto the relatively lower pressure portion of the compressed gas system,in such a way that liquids will tend to flow away from the pressurevessel. In this embodiment, the valve means is such that it can beactuated to restrict the flow of gas to between two of the threeconduits connected to the valve means, being: between the conduit to therelatively higher pressure portion of the compressed gas system and theconduit to the pneumatic cylinder; and between the conduit to thepneumatic cylinder and the conduit to the exhaust area.

[0019] In one embodiment, the piston in the pneumatic cylinder isconnected to a piston biassing means, typically a spring, which causesthe piston to tend to move so as to evacuate the compressed gas from thecylinder. The piston in the pneumatic cylinder is connected to a meansfor actuating the valve means such that when the piston is at top ofstroke, being the position of its stroke where the gas is substantiallyevacuated from the pneumatic cylinder, the valve means is actuated topermit the gas to flow from the relatively higher pressure portion ofthe compressed gas system to the pneumatic cylinder, and such that whenthe piston is substantially at bottom of stroke, the valve means isactuated to permit the compressed gas to flow from the pneumaticcylinder to the exhaust area. When the piston is at bottom of stroke,the valve means is actuated to permit the compressed gas to flow fromthe pneumatic cylinder to the exhaust area; and the piston biassingmeans causes the piston to move to top of stroke, evacuating thecompressed gas from the pneumatic cylinder to the exhaust area andthence to the relatively lower pressure portion of the compressed gassystem.

[0020] In one embodiment, the piston is connected to one end of a pistonchain. The other end of the chain is circumferentially attached to adrive sprocket. The drive sprocket is concentrically mounted on arotatable shaft passing through the wall of the pressure vessel. One endof a second chain, the return chain, is mounted circumferentially on thedrive sprocket in opposition to the piston chain. The other end of thereturn chain is attached to: the return spring; or some other biassingmeans which puts tension on the return chain. The links of the pistonchain and return chain are configured so as to engage with the sprocketteeth which are positioned around the periphery of the drive sprocket.

[0021] In use, as the pneumatic cylinder fills with compressed gas thepiston moves from top of stroke to bottom of stroke, and pulls on thepiston chain which causes the drive sprocket to rotate and whichstretches the chainspring. When the piston reaches bottom of stroke, thevalve means is actuated to permit the compressed gas in the pneumaticcylinder to vent to the exhaust area. The piston biassing means causesthe piston to move to top of stroke. This reduces the tension on thereturn spring. The return spring, through the return chain, causes thedrive sprocket to rotate in the reverse direction to its previousrotation. When the piston reaches top of stroke, the compressed gasceases venting to the exhaust area, compressed gas starts flowing intothe pneumatic cylinder and the cycle repeats itself. In this way thereciprocating motion of the piston is converted to an oscillating rotarymotion of the shaft.

[0022] It will be clear to those skilled in the art that a variety ofmeans for transforming the oscillating motion of the piston into arotary motion could be employed, including but not limited to: a rackand pinion, and a swash plate drive.

[0023] The oscillating rotary motion of the shaft may be used to drive amechanical device by converting the motion to non-oscillating rotarymotion by means of a ratchet slip clutch and a flywheel.

[0024] It will be clear to those skilled in the art that with somepneumatic devices it is possible to connect the interior of the pressurevessel to the area of higher pressure in the compressed gas systemwhereby the work environment within the pressure vessel is in fluidcontact with the area of higher pressure. With this configuration, theexhaust of the pneumatic device is connected to the area of lowerpressure in the compressed gas system and the intake of the pneumaticdevice is in fluid communication with the interior of the pressurevessel.

[0025] Typically, when the pneumatic apparatus is used with a naturalgas pipeline system it is necessary to use a differential controller tocreate the required pressure differential. The pipeline system may havea pressure differential which is either too small to drive the pneumaticapparatus or too large for the components of the pneumatic device towithstand. Differential controllers can take many forms. Typically theyhave a means for sensing the pressure upstream and downstream of avalve, these sensors being connected to a means for opening and closingthe valve, so that the valve opening is constricted when the pressuredifferential is less than desired and enlarged when the pressuredifferential is greater than desired. In natural gas pipeline systemswhere the pressure differential naturally occurring in the system is toosmall, the differential controller is installed in line in the pipelineto create the necessary pressure differential. By contrast, in naturalgas pipeline systems where the pressure differential naturally occurringin the system is too large, the differential controller is installed inline in the conduit between the pipeline system and the pneumaticapparatus to reduce the existing pressure differential.

[0026] It is clear that the pneumatic apparatus will only function whenthere is a pressure differential. In most compressed gas systems thispressure differential arises because the gas is flowing. The pressuredifferential disappears when the gas ceases to flow, even though thecompressed gas system is still pressurized. In some applications, suchas where methanol is being injected into a pipeline to act as anantifreeze, it is preferable that the methanol injection stop while thegas is not flowing. In other applications, such as where the pneumaticapparatus is being used to pump heated glycol through heat tracingpositioned around above-ground portions of a pipeline, it is preferablethat the pump continue to operate even though the gas is not flowing. Ifit is necessary to keep the pneumatic device operating whether or notthe gas is flowing the conduit connecting the interior of the pressurevessel to the compressed gas system can be fitted with a bypass to adifferential controller and thence to atmosphere.

[0027] In another embodiment of this invention, related to pressurisingthe work environment, where it is necessary to inject a liquid into acompressed gas, in a natural gas pipeline for example, enclosing theliquid in a container in which the liquid is under the same pressure asthe compressed gas, and locating that container so that the outlet forthe liquid is higher than the location where the liquid is injected intothe compressed gas, results in a gravity-induced flow of the liquid fromthe container into the compressed gas. The liquid in the vessel can bepressurized to the same pressure as the compressed gas by many means,including locating the liquid container in a larger high pressure vesselcontaining the compressed gas, or making the liquid container itself ahigh pressure vessel with sufficient connections to the compressed gasto keep the liquid at the same pressure as the compressed gas and topermit a controlled flow of the liquid into the compressed gas. The flowof liquid into the compressed gas may be controlled by way of a meteringvalve or other similar device. The level of the liquid can be monitoredwith a high-pressure level sight glass. Liquid can be added to theliquid container by a variety of means, including, a high pressure pumpif it is necessary to maintain the liquid at the same pressure as thecompressed gas, or by gravity or other simple means if it is possible toisolate the liquid container from the compressed gas and bleed it downto atmospheric pressure.

[0028] According to one aspect, the invention consists of a pneumaticapparatus for using the pressure differential between an area of higherpressure and an area of lower pressure in a compressed gas system todrive equipment, the pneumatic apparatus comprising:

[0029] (A) a pressure vessel;

[0030] (B) a gas outlet in the wall of the pressure vessel, said gasoutlet being in fluid communication with the interior of the pressurevessel;

[0031] (C) a pneumatic device, a portion of said pneumatic device beinglocated within the pressure vessel, and said pneumatic device includingan intake and an exhaust, wherein when the pneumatic device is beingpneumatically actuated, the gas used to drive the pneumatic devicepasses into the pneumatic device through the intake and the exhaust gasis exhausted through the exhaust; and

[0032] (D) said pneumatic device exhaust being in fluid communicationwith the interior of the pressure vessel;

[0033] wherein if the gas outlet is connected by suitable conduit to thearea of lower pressure whereby the interior of the pressure vessel is influid contact with the area of lower pressure and the pneumatic deviceintake is connected by suitable conduit to the area of higher pressurewhereby the pneumatic device intake is in fluid contact with the area ofhigher pressure, then exhaust gas from the pneumatic device can flow tothe area of lower pressure.

[0034] A portion of the equipment driven by the pneumatic apparatus maybe located within the pressure vessel. The equipment driven by thepneumatic apparatus may be located outside the pressure vessel.

[0035] The pneumatic device may comprise:

[0036] (A) a pneumatic cylinder;

[0037] (B) a piston within the pneumatic cylinder, said piston defininga chamber with the pneumatic cylinder, said chamber changing in size asthe piston moves within the pneumatic cylinder;

[0038] (C) a piston biassing means connected to the piston and causingthe piston to tend to move to, and remain at, top of stroke, being theposition of the piston where the chamber is the smallest;

[0039] (D) a three-port Y valve, wherein one port is connected byconduit to the chamber; one port is the pneumatic device intake and oneport is the pneumatic device exhaust;

[0040] (E) a valve switch incorporated in the Y valve wherein when thevalve switch is at a first position, gas can flow through the Y valvebetween the intake and the chamber, and when the valve switch is at asecond position gas can flow through the Y valve between the chamber andthe exhaust; and

[0041] (F) a linkage connecting the piston to the valve switch, whereinwhen the piston is substantially at top of stroke the valve switch is atthe first position and when the piston is substantially at bottom ofstroke the valve switch is at the second position,

[0042] whereby when the piston is at top of stroke, gas can flow fromthe intake to the chamber and when the piston is at bottom of stroke,gas can flow from the chamber to the exhaust.

[0043] The linkage may comprise:

[0044] (A) a rotatable member;

[0045] (B) a flexible member connected to the piston and attached to therotatable member, whereby movement of the piston in the direction fromtop of stroke to bottom of stroke will cause the rotatable member torotate in one direction;

[0046] (C) a rotatable member biassing means connected to the rotatablemember and tending to cause the rotatable member to rotate in theopposite direction from that rotation caused by the movement of thepiston in the direction from top of stroke to bottom of stroke;

[0047] (D) means for connecting the rotatable member to the valveswitch.

[0048] The rotatable member may be attached to an output shaft. Theoutput shaft may pass through the wall of the pressure vessel. Therotatable member may be a sprocket, said sprocket incorporating teeth,and the flexible member may be a chain, wherein the chain engages withthe teeth. The rotatable member biassing means may comprise a spring,one end of the spring being connected to the drive sprocket. The meansfor connecting the rotatable member to the valve switch may comprise aswitch spring.

[0049] The pressure vessel may contain a liquid. The liquid may be oil.

[0050] According to another aspect, the invention consists of apneumatic apparatus for using the pressure differential between an areaof higher pressure and an area of lower pressure in a compressed gassystem to drive equipment, the pneumatic apparatus comprising:

[0051] (A) a pressure vessel; and

[0052] (B) a pneumatic device, a portion of said pneumatic device beinglocated within the pressure vessel, and said pneumatic deviceincorporating an intake and an exhaust, wherein when the pneumaticdevice is being pneumatically actuated, the gas used to drive thepneumatic device passes into the pneumatic device through the intake andthe exhaust gas is exhausted through the exhaust,

[0053] wherein if the pneumatic device exhaust is in fluid communicationwith the area of lower pressure and the pneumatic device intake is influid communication with the area of higher pressure, then exhaust gasfrom the pneumatic device can flow to the area of lower pressure.

[0054] The interior of the pressure vessel may be in fluid communicationwith the pneumatic device exhaust. The interior of the pressure vesselmay be in fluid communication with the pneumatic device intake.

[0055] According to another aspect, the invention consists of a liquidinjection apparatus for use with a compressed gas system comprising:

[0056] (A) a liquid container connected to the compressed gas systemsuch that the interior of the liquid container is in fluid communicationwith the compressed gas system; and

[0057] (B) a conduit connecting the liquid container to an injectionpoint on the compressed gas system,

[0058] wherein liquid can flow from the liquid container to theinjection point.

[0059] The liquid injection apparatus may also comprise a pressurevessel, wherein: the liquid container is located within the pressurevessel, the interior of the liquid container is in fluid communicationwith the interior of the pressure vessel and the interior of thepressure vessel is in fluid communication with the compressed gassystem. The liquid container may be located higher than the injectionpoint on the compressed gas system.

[0060] The various features of novelty which characterize the inventionare pointed out with more particularity in the claims annexed to andforming a part of the disclosure. For a better understanding of theinvention, its operating advantages and specific objects attained by itsuse, reference should be made to the accompanying drawings anddescriptive matter in which there are illustrated and describedpreferred embodiments of the invention.

IN THE DRAWINGS

[0061]FIG. 1 is an elevation view of the pneumatic apparatus withexternal drive with parts of the pressure vessel wall and the pneumaticcylinder cut away, showing the piston at the top of its stroke;

[0062]FIG. 2 is an elevation view of the pneumatic apparatus withexternal drive, with parts of the pressure vessel wall and the pneumaticcylinder cut away, showing the piston at the bottom of its stroke;

[0063]FIG. 3 is an external view of the pneumatic apparatus showing theexternal drive;

[0064]FIG. 4 is an elevation view of the pneumatic apparatus withinternal pump, with parts of the pressure vessel wall and the pneumaticcylinder cut away, showing the piston at the top of its stroke;

[0065]FIG. 5 is an elevation view of the pneumatic apparatus withinternal pump, with parts of the pressure vessel wall and the pneumaticcylinder cut away, showing the piston at the bottom of its stroke;

[0066]FIG. 6 is a schematic view of the liquid-injection apparatus;

[0067]FIG. 7 is an elevation view of one embodiment of the invention,with parts of the pressure vessel wall, the pneumatic cylinder and theoutlet pipe, cut away, showing the piston at top of stroke;

[0068]FIG. 8 is the same view as FIG. 7, showing the piston at bottom ofstroke; and

[0069]FIG. 9 is an elevation view of the side of the embodiment shown inFIGS. 7 and 8, with the pressure vessel wall, the trunnion and part ofthe outlet pipe, cut away, showing the piston at top of stroke.

DETAILED DESCRIPTION OF THE INVENTION

[0070] Referring to FIGS. 1 and 2, a pneumatic apparatus with externaldrive (10) is shown comprising a pressure vessel (12) connected to thecompressed gas outlet (16) and containing several components. One of thecomponents is a pneumatic cylinder (32) containing a piston (34) whichis connected to the piston shaft (28). The piston shaft (28) isconnected to one end of the piston shaft chain (24). The other end ofthe piston shaft chain (24) is circumferentially attached to the wheel(22) and some additional portion of the piston shaft chain (24) is incontact with the edge of the wheel (22) such that movement of the pistonshaft (28) away from the wheel (22) will cause the wheel (22) to rotate.The wheel (22) is concentrically attached to the output shaft (38). TheY valve switch operators (23 a and 23 b) are attached to the side of thewheel (22). One end of the spring chain (26) is circumferentiallyattached to the wheel (22). The other end of the spring chain (26) isattached to the spring (30) and some additional portion of the springchain (26) is in contact with the edge of the wheel (22) such thatmovement of the part of the spring (28)connected to the spring chain(26) away from the wheel (22) will cause the wheel (22) to rotate. The Yvalve (18) is positioned adjacent to the wheel (22) such that the Yvalve switch operators (23) contact the Y valve switch (20) when thewheel (22) rotates. The Y valve is connected to the compressed gas inlet(14), the valve to cylinder conduit (33) and the valve to interiorconduit (35).

[0071] The pressure vessel (12) is filled with sufficient oil (17) suchthat substantially all of the components contained in the pressurevessel (12) are below the top of oil (19) and are submerged in the oil(17). The piston seal (36) and piston shaft seal (31) act to exclude theoil (17) from the pneumatic cylinder (32).

[0072] The compressed gas outlet (16) and the compressed gas inlet (14)are each connected to a point on a compressed gas system. The compressedgas system has pressure differentials within it. The compressed gasoutlet (16) is connected to a point on the compressed gas system wherethe pressure is lower than the pressure at the point where thecompressed gas inlet (14) is connected to the compressed gas system. Thecompressed gas outlet (16) is open to the interior of the pressurevessel (12) and therefore the interior of the pressure vessel (12) is atsubstantially the same pressure as the point on the compressed gassystem where the compressed gas outlet (16) is connected.

[0073] Referring to FIG. 1, the piston (34) is at the top of its strokeand the wheel (22) is in a position whereby one of the Y valve switchoperators (2 a) is in contact with the Y valve switch (20). The Y valveswitch (20) is in the position whereby the Y valve (18) is only openbetween the compressed gas inlet (14) and the valve to cylinder conduit(33), which permits a flow of compressed gas from the compressed gasinlet (14) to the valve to cylinder conduit (33) and thereby into thepneumatic cylinder (32). As the compressed gas flows into the pneumaticcylinder (32) the pressure on the compressed gas side of the piston (34)tends to exceed the pressure on the other side of the piston (34)generating a force against the piston (34). When that force exceeds theresistence of the spring (30), the spring begins to stretch and thepiston (34) begins to move towards the bottom of its stroke.

[0074] When the piston (34) reaches the bottom of its stroke, FIG. 2,the wheel (22) has been rotated by the movement of the piston (34)through the connection with the piston chain (24) and piston shaft (28),such that the other Y valve switch operator (23b) contacts the Y valveswitch (20) and moves the Y valve switch (20) so that the Y valve (18)is only open between the valve to interior conduit (35) and the valve tocylinder conduit (33), which permits a flow of compressed gas from thepneumatic cylinder (32), through the valve to cylinder conduit (33),through the valve to interior conduit (35) and into the interior of thepressure vessel, whereby the pressure within the pneumatic cylinder (32)drops to equalize with the pressure in the remainder of the interior ofthe pressure vessel (12). As the pressure in the pneumatic cylinder (32)drops, the force against the piston (34) decreases to a point where itis less than the resistence of the spring (30) imparted via the springchain (26), wheel (22), piston chain (28) and piston shaft (28), and thepiston (34) moves towards the top of its stroke. When the piston (34)reaches the top of its stroke, FIG. 1, a Y valve switch operator (23 a)contacts and moves the Y valve switch (20) to the position whereby the Yvalve (18) is only open between the compressed gas inlet (14) and thevalve to cylinder conduit (33), and the piston (34) begins anotherstroke.

[0075] In this way, each cycle of the piston (34), from top of stroke,FIG. 1, to bottom of stroke, FIG. 2, and back again, FIG. 1, causes thewheel (22) to rotate first in one direction and then in the otherdirection. The wheel (22) is fixed to the output shaft (38). The outputshaft (38) undergoes the same oscillating rotary motion as the wheel(22). The output shaft (38) projects through the wall of the pressurevessel (12), FIG. 3, and is sealed with a suitable seal (not shown). Theoutput shaft (38) can be used to drive a variety of mechanical devices.

[0076] Referring to FIGS. 4 and 5, a pneumatic apparatus with internalpump (41) is shown. An embodiment of the invention with a configurationof spring (30), spring chain (26), wheel (22), piston shaft chain (24)and piston shaft (28), which is similar to the previously describedpneumatic apparatus with external drive, is shown. However, such aconfiguration is not essential to the invention. The invention canfunction with a variety of configurations comprising a pressure vessel;a pneumatic drive unit; a pump; and a means of connecting the pneumaticdrive unit to the pump.

[0077] The pressure vessel (12) is filled with sufficient oil (17) suchthat substantially all of the components contained in the pressurevessel (12) are below the top of oil (19) and are submerged in the oil(17). The piston seal (36) and piston shaft seal (31) act to exclude theoil (17) from the pneumatic cylinder (32).

[0078] The embodiment of the invention shown in FIGS. 4 and 5, operatesto create a reciprocating movement of the piston (34) in the same manneras the previously described pneumatic apparatus with external drive, butit is different in that the wheel axis of rotation (43) is notnecessarily an output shaft. The piston (34) is connected to the pump(42) by way of the pump drive shaft (48). The pump is connected to aliquid inlet (44) and a liquid outlet (46). The liquid inlet (44) andliquid outlet (46) pass through the wall of the pressure vessel (12).The liquid inlet (44) is connected to a supply of the liquid to beinjected (not shown). The liquid outlet (46) is connected to whateverthe liquid is being pumped to, for example a compressed gas system wherethe liquid is being injected (not shown).

[0079] The reciprocating movement of the piston (34) drives the pump(42), which pumps the liquid from the liquid inlet (44) to the liquidoutlet (46).

[0080] Referring to FIG. 6, an embodiment of the liquid injectionapparatus is shown. A gas processing pressure vessel (52) is connectedto an upstream pipeline (68) and a downstream pipeline (70). The gasprocessing pressure vessel (52) can contain means for processing the gaswithin it (not shown), for example, it may be a dehydrator. The gasprocessing pressure vessel (52) contains the liquid container (54). Theliquid container (54) contains a liquid (55). The liquid container (54)is connected to the liquid injection line (62). The liquid injectionline passes through the wall of the gas processing pressure vessel andconnects to the downstream pipeline (70). The metering valve (64) andthe meter (66) are on the liquid injection line (62). The liquid fillline (56) passes through the wall of the gas processing pressure vesseland empties into the liquid container (54). The shut-off valve (58) ison the liquid fill line (56). The liquid container is connected bysuitable conduit passing through the wall of the gas processing pressurevessel (52) to the level sight glass (62).

[0081] The liquid container (54) is filled with the liquid (55) by meansof the liquid fill line (56). When filling is not taking place theshut-off valve (58) is closed so as to maintain the pressure of thecompressed gas in the gas processing pressure vessel (52). It isapparent that there are many other means of filling the liquidcontainer, such as through the liquid injection line (62) with theaddition of a T fitting and valve (not shown). The level sight glass(60) or other suitable device can be used to monitor the level of theliquid (55) in the liquid container (54).

[0082] The interior of the liquid container (54) is exposed to the samepressure as the exterior of the liquid container (54) by suitable means.Therefore, the liquid (55) in the liquid container (54) is under thesame pressure as the compressed gas flowing in the pipeline (68 and 70)and filling the gas processing pressure vessel (54). The liquid.(55) inthe liquid container (54) can flow by gravity into the liquid injectionline (62) into the downstream pipeline (70). The metering valve (64) canbe used to control the flow of liquid into the downstream pipeline (70).The meter (66) can be used to monitor the flow of liquid into thedownstream pipeline (70).

[0083] A further embodiment of the invention is shown in FIGS. 7, 8 and9. The pneumatic apparatus (110) comprises a pressure vessel (112)containing a pneumatic device (113). A trunnion (114) is attached to,and passing through, the side of the pressure vessel (112). Thecomponents of the pneumatic device include a main bracket (116), apneumatic cylinder (118), a Y valve (120) and a drive sprocket (126).The pneumatic cylinder (118) and Y valve (120) are mounted on the mainbracket (116). The trunnion (114) passes through, and is attached to,the main bracket (116). The trunnion (114) has a trunnion bore (122) inwhich the output shaft (124) is disposed. The drive sprocket (126) isconcentrically mounted on the output shaft (124).

[0084] In the embodiment shown in FIGS. 7, 8 and 9, the pressure vessel(112) comprises the body (128) and the blind flange (130). The body(128) has a body flange (132) to which the blind flange (130) is bolted(bolts not shown) when the apparatus is in use. A gasket (134) ispositioned between the blind flange (130) and the body flange (132). Theblind flange (130) has a gas inlet (136) and a gas outlet (138). It willbe clear to persons skilled in the art that the pressure vessel (112)can take many different forms.

[0085] The gas inlet (136) is a port through the blind flange (130). Onthe top of the blind flange (130), the gas inlet (136) is, when in use,connected by suitable conduit, the inlet pipe (140), to the relativelyhigher pressure area in a compressed gas system. In the interior of thepressure vessel (112), the gas inlet (136) is connected by the inletconduit (141) to the pneumatic device intake (143) on the Y valve (120).The gas outlet (138) is a port through the blind flange (130). On thetop of the blind flange (130), the gas outlet (138) is, when in use,connected by suitable conduit, the outlet pipe (142), to the relativelylower pressure area in a compressed gas system. In this way, theinterior of the pressure vessel (112) is in fluid contact with therelatively lower pressure area in the compressed gas system and istherefore at substantially the same pressure. The inlet pipe (140) andthe outlet pipe (142) are typically metal pipe. In FIGS. 7, 8 and 9,screwed pipe is shown.

[0086] As shown in FIG. 9, the trunnion (114) is screwed into a threadedtrunnion port (144). The trunnion (114) contains two bushings (146)within which the output shaft (124) rotates. The bushings (146) must bemade of a material which will not, under the normal working pressure inthe interior of the pressure vessel (112), absorb gas or liquid so as toswell and bind between the trunnion (114) and the output shaft (124).Bushings made of polyetheretherketone are suitable for working pressuresof at least 1,000 pounds per square inch. Output shaft seals (148) aredisposed within the trunnion (114) and around the output shaft (124).The output shaft seals (148) stop gas from leaking from the pressurevessel (112) between the trunnion (114) and the output shaft (124),while permitting the output shaft (124) to rotate.Commercially-available, urethane-based, hydraulic ram seals are suitablefor the output shaft seals (148).

[0087] The drive sprocket (126) has a concentric bore (not shown) sizedto slide over the output shaft (124). The concentric bore of the drivesprocket (126) and the exterior of the output shaft (124) each have akey way (not shown). A key (not shown) is inserted into the key way toprevent the drive sprocket (126) and output shaft (124) from rotatingrelative to each other. A set screw (not shown) in the hub of the drivesprocket (126) is used to prevent the drive sprocket (126) from movinglengthwise on the output shaft (124). In use, the pressure in theinterior of the pressure vessel (112) may be several hundred pounds persquare inch greater than the exterior ambient air pressure. Pressuredifferentials of this magnitude will result in a force of severalhundred pounds tending to push the output shaft (124) out of thepressure vessel (112). To deal with this force, one end of the bore inthe drive sprocket (126) has a circumferential counter bore (not shown),and the output shaft (124) has a circumferential groove (not shown). Thecounter bore and groove are sized and positioned to contain a split ring(not shown), wherein the split ring is positioned in the groove and thedrive sprocket (126) is slid into position on the output shaft (124) andfixed in position with the set screw so as to retain the split ring. Athrust bearing (150) is disposed between the trunnion (114) and thedrive sprocket (126). In this way, the force pushing the output shaft(124) out of the pressure vessel (112) bears against the split ring. Inaddition, a safety nut (152) is threaded on to the output shaft (124) incase the thrust bearing (150) and split ring fail.

[0088] The pneumatic cylinder (118) contains a piston (160). The piston(160) has a piston seal (162) around its periphery which abuts theinterior of the pneumatic cylinder (118) through the full range ofmovement of the piston (160). The piston seal (162) acts to seal thechamber (164) defined by the piston (160) and the pneumatic cylinder(118) from the rest of the interior of the pressure vessel (112).

[0089] The piston (160) is in contact with the piston spring (166). Thepiston spring (166) is contained between the piston spring housing (168)and the piston (160). The piston spring (166) is under compression andthe piston spring (166) causes the piston (160) to tend to move towardstop of stroke, which position of the piston (160) is shown in FIG. 7.

[0090] The piston (160) is attached to one end of the ram (170). The ram(170) passes through the ram seal (172) at the end of the pneumaticcylinder (118). The ram seal (172) acts to seal the chamber (164) fromthe rest of the interior of the pressure vessel (112).

[0091] The other end of the ram (170) is connected to one end of thepiston chain (180). The other end of the piston chain (180) iscircumferentially attached to the drive sprocket (126). The drivesprocket (126) has teeth (182) spaced evenly around its periphery. Thelinks of the piston chain (180) and the teeth (182) are sized to engagewith each other. Some portion of the links of the piston chain (180)proximate to the end of the piston chain (180) which is attached to thedrive sprocket (126) are engaged with the teeth (182). Movement of theram (170) away from the drive sprocket (126) will cause the drivesprocket (126) to rotate in a clockwise direction, as the drive sprocket(126) is shown in FIGS. 7 and 8.

[0092] A second chain, the return chain (184), is circumferentiallyattached to the drive sprocket (126). The links of the return chain(184) and the teeth (182) are sized to engage with each other. Someportion of the links of the return chain (184) proximate to the end ofthe return chain (184) which is attached to the drive sprocket (126) areengaged with the teeth (182). The end of the return chain (184) which isnot attached to the drive sprocket (126) is attached to one end of thereturn spring (186). The other end of the return spring (186) isattached to the exterior of the pneumatic cylinder (118). The returnspring (186) is under tension, such that the force exerted by the returnspring (186) on the drive sprocket (126) through the return chain (184),causes the drive sprocket (126) to tend to rotate in a counterclockwisedirection, as the drive sprocket (126) is shown in FIGS. 7 and 8.

[0093] The Y valve (120) is connected to: the inlet conduit (141), thepneumatic cylinder conduit (190) and the exhaust area conduit (192). Theinlet conduit (141) connects the pneumatic device intake (143) to thegas inlet (136). The inlet conduit (141) is typically metal tubing. Thepneumatic cylinder conduit (190) connects the Y valve (120) to thechamber (164). The pneumatic cylinder conduit (190) is typically metaltubing.

[0094] The exhaust area conduit (192) connects the pneumatic deviceexhaust (193) on the Y valve (120) to the exhaust area (194). In use,exhaust area (194) is an area which is in fluid communication with therelatively lower pressure portion of the compressed gas system. In FIGS.7, 8 and 9, the exhaust area (194) is within the outlet pipe (142). Thisconfiguration prevents any liquids which might be mixed with thecompressed gas from being deposited within the pressure vessel (112). Ifthere is no concern about liquids or other matter being deposited in thepressure vessel (112), the exhaust area (194) can be within the pressurevessel (112). If the exhaust area is within the outlet pipe (142), theexhaust area conduit (192) is typically flexible tubing to facilitatefitting it within the outlet pipe (142). If the exhaust area (194) iswithin the pressure vessel (112), the exhaust area conduit (192) istypically rigid tubing.

[0095] The Y valve (120) is actuated by moving the valve switch (200)between the left stop (202) and the right stop (204). As with thedirections of rotation of the drive sprocket (126), “left” and “right”are used solely for convenience in explaining the parts of the inventionas shown in the views in FIGS. 7 and 8. When the valve switch (200) isproximate to the left stop (202), gas can flow from the gas inlet (136),through the Y valve (120) and into the chamber (164). When the valveswitch (200) is proximate to the right stop (204), gas can flow from thechamber (164), through the Y valve (120) and to the exhaust area (194).

[0096] The valve switch (200) is controlled by the switch operator(206). The switch operator (206) is attached to the side of the drivesprocket (126) adjacent to the Y valve (120). The switch operator (206)is connected to one end of the switch spring (208) at the operator pin(210). The valve switch (200) is connected to the other end of theswitch spring (208) at the switch pin (212). The switch spring (208) isunder tension. As is apparent in FIGS. 7 and 8, the position which theoperator pin (210) must be in for the switch operator (206) to move thevalve switch (200), is defined by a line passing through the center ofthe switch pin (212) and the center of the switch pivot (214). Forexample, if, as shown in FIG. 7, the operator pin (210) is to the leftof the line defined by the switch pin (212) and the switch pivot (214),and the valve switch (200) is against the left stop (202), then theswitch operator (206) will not exert a rightward pull on the valveswitch (200) until the operator pin (210) is to the right of the linedefined by the switch pin (212) and the switch pivot (214), at whichtime the operator pin (210) will be in position to pull the valve switch(200) against the right stop (204). It is clear that the same applies tothe reverse motion of the switch operator (206) and valve switch (200).In this way, a reciprocal motion of the drive sprocket (126) causes theY valve (120) to be positively switched from one position to another.

[0097] Typically, the pressure vessel (112) is filled with sufficientoil (220) such that substantially all of the components contained in thepressure vessel (112) are below the top of oil (222) and are submergedin the oil (220). A dipstick assembly (not shown), comprising a threadedport in the top of the pressure vessel (112); a threaded plug rated forthe working pressure of the apparatus; and a marked rod attached to thethreaded plug, may be installed to monitor the level of the oil (220)within the pressure vessel (112).

[0098] In use, as described above, the gas inlet (136) is connected bysuitable conduit to a relatively higher pressure area in a compressedgas system, and the gas outlet (138) is connected by suitable conduit toa relatively lower pressure area in the compressed gas system. Thepressure differential between the higher pressure and lower pressuregas, drives the piston (160) in the power stroke, being from top ofstroke to bottom of stroke, and the piston spring (166) and the returnspring (186) drive the piston (160) in the exhaust stroke, being frombottom of stroke to top of stroke.

[0099]FIG. 7 shows the position of the various components just after theend of the exhaust stroke: the piston (160) is at top of stroke; thedrive sprocket (126) has been rotated counterclockwise by the forceexerted by the return spring (186); and the switch operator (206) haspulled the valve switch (200) against the left stop (202), therebypermitting gas to flow from the gas inlet (136) to the chamber (164). Asthe relatively higher pressure compressed gas flows into the chamber(164), the pressure within the chamber (164) increases until it isgreater than the pressure on the other side of the piston (160), whichresults in a force against the piston (160). Movement of the piston(160) is resisted by a variety of factors, including: the resistence ofthe piston spring (166) and the return spring (186); friction; and theresistence of the device which the pneumatic apparatus (110) is driving.When the force against the piston (160) exceeds this resistence thepiston (160) begins to move towards bottom of stroke, compressing thepiston spring (166) and stretching the chain spring (186).

[0100] When the piston (160) reaches bottom of stroke, FIG. 8, thepiston chain (180) has rotated the drive sprocket (126) such that theoperator pin (210) has moved sufficiently so that the valve switch (200)has been pulled against the right stop (204). In this position, the Yvalve (120) permits gas to flow from the chamber (164) to the exhaustarea (194). The pressure within the chamber (164) equalizes with thepressure in the exhaust area (194), which is substantially the same asthe pressure within the pressure vessel (112) and in the lower pressureportion of the gas system. As the pressure in the chamber (164) drops,the force against the piston (160), resulting from the difference inpressure on either side of the piston (160) decreases to a point whereit is less than the force applied by the piston spring (166) and thereturn spring (186), and the piston (160) begins to move toward top ofstroke. As the piston (160) reaches top of stroke, the switch operator(206) will pull the valve switch (200) to the left stop (202), thecomponents of the apparatus will once again be in the position shown inFIG. 7, and the cycle will repeat itself.

[0101] In this way, each cycle of the piston (160), from top of stroke,FIG. 7, to bottom of stroke, FIG. 8, and back again, FIG. 7, causes thedrive sprocket (126) and the output shaft (124) to rotate first in onedirection and then in the other direction. As will be obvious to thoseskilled in the art, the output shaft (124) can be used to drive avariety of mechanical devices in a variety of different ways, including,but not limited to: attaching a crank (224) to the shaft as shown inFIGS. 7, 8 and 9; and by converting the oscillating rotary motion of theoutput shaft (124) to non-oscillating rotary motion by means of aratchet slip clutch and flywheel (not shown).

[0102] The foregoing is a description of a preferred embodiment of theinvention which is given here by way of example. The invention is not tobe taken as limited to any of the specific features as described, butcomprehends all such variations thereof as come within the scope of theappended claims.

What is claimed is:
 1. A pneumatic apparatus for using the pressuredifferential between an area of higher pressure and an area of lowerpressure in a compressed gas system to drive equipment, the pneumaticapparatus comprising: (A) a pressure vessel; (B) a gas outlet in thewall of the pressure vessel, said gas outlet being in fluidcommunication with the interior of the pressure vessel; (C) a pneumaticdevice, a portion of said pneumatic device being located within thepressure vessel, and said pneumatic device including an intake and anexhaust, wherein when the pneumatic device is being pneumaticallyactuated, the gas used to drive the pneumatic device passes into thepneumatic device through the intake and the exhaust gas is exhaustedthrough the exhaust; and (D) said pneumatic device exhaust being influid communication with the interior of the pressure vessel; wherein ifthe gas outlet is connected by suitable conduit to the area of lowerpressure whereby the interior of the pressure vessel is in fluid contactwith the area of lower pressure and the pneumatic device intake isconnected by suitable conduit to the area of higher pressure whereby thepneumatic device intake is in fluid contact with the area of higherpressure, then exhaust gas from the pneumatic device can flow to thearea of lower pressure.
 2. The pneumatic apparatus of claim 1 wherein aportion of the equipment driven by the pneumatic apparatus is locatedwithin the pressure vessel.
 3. The pneumatic apparatus of claim 1wherein the equipment driven by the pneumatic apparatus is locatedoutside the pressure vessel.
 4. The pneumatic apparatus of claim 1wherein the pneumatic device comprises: (A) a pneumatic cylinder; (B) apiston within the pneumatic cylinder, said piston defining a chamberwith the pneumatic cylinder, said chamber changing in size as the pistonmoves within the pneumatic cylinder; (C) a piston biassing meansconnected to the piston and causing the piston to tend to move to, andremain at, top of stroke, being the position of the piston where thechamber is the smallest; and (D) a three-port Y valve, wherein one portis connected by conduit to the chamber; one port is the pneumatic deviceintake and one port is the pneumatic device exhaust; (E) a valve switchincorporated in the Y valve wherein when the valve switch is at a firstposition, gas can flow through the Y valve between the intake and thechamber, and when the valve switch is at a second position gas can flowthrough the Y valve between the chamber and the exhaust; and (F) alinkage connecting the piston to the valve switch, wherein when thepiston is substantially at top of stroke the valve switch is at thefirst position and when the piston is substantially at bottom of strokethe valve switch is at the second position, whereby when the piston isat top of stroke, gas can flow from the intake to the chamber and whenthe piston is at bottom of stroke, gas can flow from the chamber to theexhaust.
 5. The pneumatic apparatus of claim 4 wherein the linkagecomprises: (A) a rotatable member; (B) a flexible member connected tothe piston and attached to the rotatable member, whereby movement of thepiston in the direction from top of stroke to bottom of stroke willcause the rotatable member to rotate in one direction; (C) a rotatablemember biassing means connected to the rotatable member and tending tocause the rotatable member to rotate in the opposite direction from thatrotation caused by the movement of the piston in the direction from topof stroke to bottom of stroke; and (D) means for connecting therotatable member to the valve switch.
 6. The pneumatic apparatus ofclaim 5 wherein the rotatable member is attached to an output shaft. 7.The pneumatic apparatus of claim 6 wherein the output shaft passesthrough the wall of the pressure vessel.
 8. The pneumatic apparatus ofclaim 5 wherein the rotatable member is a sprocket, said sprocketincorporating teeth, and the flexible member is a chain, wherein thechain engages with the teeth.
 9. The pneumatic apparatus of claim 8wherein the rotatable member biassing means comprises a spring, one endof the spring being connected to the drive sprocket.
 10. The pneumaticapparatus of claim 5 wherein the means for connecting the rotatablemember to the valve switch comprises a switch spring.
 11. The pneumaticapparatus of claim 1 wherein the pressure vessel contains a liquid. 12.The pneumatic apparatus of claim 11 wherein the liquid is oil.
 13. Apneumatic apparatus for using the pressure differential between an areaof higher pressure and an area of lower pressure in a compressed gassystem to drive equipment, the pneumatic apparatus comprising: (A) apressure vessel; and (B) a pneumatic device, a portion of said pneumaticdevice being located within the pressure vessel, and said pneumaticdevice incorporating an intake and an exhaust, wherein when thepneumatic device is being pneumatically actuated, the gas used to drivethe pneumatic device passes into the pneumatic device through the intakeand the exhaust gas is exhausted through the exhaust, and wherein if thepneumatic device exhaust is in fluid communication with the area oflower pressure and the pneumatic device intake is in fluid communicationwith the area of higher pressure, then exhaust gas from the pneumaticdevice can flow to the area of lower pressure.
 14. The pneumaticapparatus of claim 13 wherein the interior of the pressure vessel is influid communication with the pneumatic device exhaust.
 15. The pneumaticapparatus of claim 13 wherein the interior of the pressure vessel is influid communication with the pneumatic device intake.
 16. A liquidinjection apparatus for use with a compressed gas system comprising: (A)a liquid container connected to the compressed gas system such that theinterior of the liquid container is in fluid communication with thecompressed gas system; and (B) a conduit connecting the liquid containerto an injection point on the compressed gas system, wherein liquid canflow from the liquid container to the injection point.
 17. The liquidinjection apparatus of claim 16 further comprising a pressure vessel,wherein: the liquid container is located within the pressure vessel, theinterior of the liquid container is in fluid communication with theinterior of the pressure vessel and the interior of the pressure vesselis in fluid communication with the compressed gas system.
 18. The liquidinjection apparatus in claim 16 wherein the liquid container is locatedhigher than the injection point on the compressed gas system.